18 research outputs found
A Modified Neural Network system based on Morphological operations for detection of images with variation in Gray level intensity and facial expressions
We introduce an algorithm based on the morphological shared-weight neural network. Which extract the features and then classify them. This type of network can work effectively, even if the gray level intensity and facial expression of the images are varied. The images are processed by a morphological shared weight neural network to detect and extract the features of face images. For the detection of the edges of the image we are using sobel operator. We are using back propagation algorithm for the purpose of learning and training of the neural network system. Being nonlinear and translation-invariant, the morphological operations can be used to create better generalization during face recognition. Feature extraction is performed on grayscale images using hit-miss transforms that are independent of gray-level shifts. The recognition efficiency of this modified network is about 98%
Multi-band superconductivity driven by a site-selective mechanism in MoGa
The family of the endohedral gallide cluster compounds recently emerged as a
new family of superconductors which is expected to host systems displaying
unconventional physics. MoGa is an important member of this family
which shows relatively large 10 K and has shown indications of
strong electron-phonon coupling and multi-band superconductivity. Here, through
direct measurement of superconducting energy gap by scanning tunneling
spectroscopy (STS) we demonstrate the existence of two distinct superconducting
gaps of magnitude 0.85 meV and 1.6 meV respectively in MoGa. Both
the gaps are seen to be conventional in nature as they evolve systematically
with temperature as per the predictions of BCS theory. Our band structure
calculations reveal that only two specific Mo sites in an unit cell contribute
to superconductivity where only / and orbitals
have strong contributions. Our analysis indicates that the site-elective
contribution govern the two-gap nature of superconductivity in MoGa.Comment: 6 pages, 5 figure
Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor SbSe
Majority of the AB type chalcogenide systems with strong spin-orbit
coupling, like BiSe, BiTe and SbTe etc., are
topological insulators. One important exception is SbSe, where a
topological non-trivial phase was argued to be possible under ambient
conditions, but such a phase could be detected to exist only under pressure. In
this Letter, we show that like BiSe, SbSe, displays generation
of highly spin-polarized current under mesoscopic superconducting point
contacts as measured by point contact Andreev reflection spectroscopy. In
addition, we observe a large negative and anisotropic magnetoresistance in
SbSe, when the field is rotated in the basal plane. However, unlike in
BiSe, in case of SbSe a prominent quasiparticle interference
(QPI) pattern around the defects could be obtained in STM conductance imaging.
Thus, our experiments indicate that SbSe is a regular band insulator
under ambient conditions, but due to it's high spin-orbit coupling, non-trivial
spin-texture exists on the surface and the system could be on the verge of a
topological insulator phase.Comment: 5 pages, 4 figures, supplemental material not include
Generation of strain-induced pseudo-magnetic field in a doped type-II Weyl semimetal
In Weyl semimetals, there is an intriguing possibility of realizing a
pseudo-magnetic field in presence of small strain due to certain special cases
of static deformations. This pseudo-magnetic field can be large enough to form
quantized Landau levels and thus become observable in Weyl semimetals. In this
paper, we experimentally show the emergence of a pseudo-magnetic field (~ 3
Tesla) by Scanning Tunneling Spectroscopy (STS) on the doped Weyl semimetal
Re-MoTe2, where distinct Landau level oscillations in the tunneling conductance
are clearly resolved. The crystal lattice is intrinsically strained where large
area STM imaging of the surface reveals differently strained domains where
atomic scale deformations exist forming topographic ripples with varying
periodicity in the real space. The effect of pseudo-magnetic field is clearly
resolved in areas under maximum strain.Comment: 6 pages, 4 figure
High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb
CuFeSb is isostructural to the ferro-pnictide and chalcogenide
superconductors and it is one of the few materials in the family that are known
to stabilize in a ferromagnetic ground state. Majority of the members of this
family are either superconductors or antiferromagnets. Therefore, CuFeSb may be
used as an ideal source of spin polarized current in spin-transport devices
involving pnictide and the chalcogenide superconductors. However, for that the
Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper
we report direct measurement of transport spin polarization in CuFeSb by
spin-resolved Andreev reflection spectroscopy. From a number of measurements
using multiple superconducting tips we found that the intrinsic transport spin
polarization in CuFeSb is high ( 47\%). In order to understand the unique
ground state of CuFeSb and the origin of large spin polarization at the Fermi
level, we have evaluated the spin-polarized band structure of CuFeSb through
first principles calculations. Apart from supporting the observed 47\%
transport spin polarization, such calculations also indicate that the Sb-Fe-Sb
angles and the height of Sb from the Fe plane is strikingly different for
CuFeSb than the equivalent parameters in other members of the same family
thereby explaining the origin of the unique ground state of CuFeSb.Comment: 6 pages, 4 figure